There's no kind of middle ground?? Like bomb their military bases and cripple their ability to launch attacks? Then blockade their land until they are forced to surrender?

No, that wouldn't work. If we bombed their military bases, we'd need fighters to escort them, and then we'd need to counter their aircraft and the ground-based units that can destroy planes. Aircraft alone can't make a nation submit (the blitz is hard proof of this), and we'd need ground support to help do the job. And sending in troops and planes to destroy their military bases counts as a full-scale invasion.

Blockading wouldn't work either. Japan is too large to effectively blockade, and they could be self-sufficient if they were determined to. Given how fanatical the Japanese were, that seems likely... If the fact that they were the only country left practically fighting off the world wouldn't convince them to surrender, I doubt a blackade could.